The disclosure relates to turbine engine. More particularly, the disclosure relates to bonding galvanically dissimilar sheaths and substrates.
In a number of situations in gas turbine engine cold section components such as blades and vanes, a protective sheath is used to protect a substrate or main body of the component. Such sheaths may offer protection from foreign object damage or wear to leading edge and/or trailing edge portions of airfoils. In such situations, the sheath forms a limited portion of the airfoil contour with the main body providing the rest.
In some examples, the sheath may be of a more expensive material than the main body (e.g., a titanium alloy sheath on an aluminum alloy body where the aluminum alloy is used for cost reasons). In others, the sheath may be of a less expensive material (e.g., when the body is of a very light material with little impact resistance (e.g., a carbon fiber composite)).
US patent application publications 20110211967 and 20120301292 disclose a sheath bonded to blade substrate using a scrim and epoxy. The scrim and epoxy may galvanically isolate the sheath from the substrate to prevent corrosion.